<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <link rel="stylesheet" href="homework01.css"/>
    <style type="text/css">
        #homework002{
            background-color: #00FF00;
            font-size: 2em;
            text-align: center;
        }
    </style>
</head>
<body>
<div>
    <h1 id="homework001">测试01</h1>
    <h1 style="background-color: #00FFFF;font-size: 2em;text-align: center;">测试02</h1>
    <h1 id="homework002">测试03</h1>
</div>
</body>
</html>